Alkyl orthosilicate and alkoxysiloxane base grease compositions



iatented June 15, 1954 2,681,313 ALKYL ORTHOSILICATE AND ALKOXY- SILOXANE TIONS BASE GREASE COMPOSI- William S. Kather, San Carlos, and Tibor Wiener, Palo Alto, Calif., assignors, by mesne assignments, to California Res Francisco, Calif.,

N Drawing. Application earch Corporation, San a corporation of Delaware February 20, 1950,

Serial No. 145,306

12 Claims.

, This invention relates to lug compositions made or alkoxysiloxanes.

Greases prepared from mineral oils have many limitations, particularly where satisfactory lubrication is required at both high and low temperatures. Mineral oil greases can be made to have satisfactory low torque requirements at low temperatures for use in outdoor equipment and in aircraft, but the compositions are extremely volatile and have poor oxidative stability resulting in a short service life. Conversely, mineral oil greases with suitable high temperature properties are too stiff to render service at temperatures much below F. Because of the narrow temperature range of petroleum oils, recent work has been directed toward the preparation of greases using various synthetic fluids, and one such group, the branched-chain alkyl diesters of dicarboxylic acids as disclosed in Zisman et a1. Patent Number 2,448,567, has shown improvement over mineral oil greases.

The alkyl orthosilicates and the alkyl diesters of dicarboxylic acids possess similar advantages over mineral oils. However, in comparing the two groups of synthetic fluids where the hydrocarbon radicals are identical, we have found that the alkyl orthosilicates possess superior thermal stability, higher viscosity indices, and better hydrolytic stability than the corresponding alkyl diesters of dicarboxylic acids. A large homologous series of the latter fluids are known, and more viscous liquids may be selected for formulation when heavy-duty greases are desired. However, the more viscous members of the series have undesirably high pour points for low-temperature use as fluids or greases, and their viscosity index is as undesirably low as that of some mineral oils.

In contrast thereto, most of the alkoxysiloxanes which are described and claimed in our copending application, Serial Number 137,264, filed January 6, 1950, owned by the common assignee of these applications, have an extremely low pour point and a high viscosity index. Each also has a high boiling range, a high flash and fire point, a low vapor pressure, good thermal and hydrolytic stability, and excellent lubricating characteristics. These alkoxysiloxanes have the further advantage of possessing outstanding oxidative stability, in the presence of inhibitors, which is superior to any known fluids with the possible exception of the expensive alkylsiloxanes.

These desirable physical properties of the alkyl orthosilicatesand the alkoxysiloxanes may be grease type lubricatwith alkyl orthosilicates A further object of this invention is to provide inhibitors for stabilizing such greases against oxidation.

Another and still further object is to provide such greases in which the alkyl orthosilicates and the alkoxysiloxanes are substantial components.

Other and further objects will be apparent from the following description of this invention.

We have discovered that compositions com posed in major portion of an alkyl orthosilicate, an alkoxysiloxane, or mixtures thereof, together with smaller proportions of an alkali metal soap, yield superior grease compositions when the constituents are properly blended and inhibited. In selecting the particular alkyl orthosilicate or alkoxysiloxane, any aliphatic radical ranging from higher may be used, although there are disadvantages in either extremity of the aliphatic series. The very short aliphatic radicals from methyl greases, we prefer to use branched chain aliphatic radicals, particularly those whose branching occurs on a carbon atom close to the silicon nucleus so that a greater degree of steric hindrance is provided. Radicals such as l-ethylpropyl, 2-ethy1butyl, 1,3-dimethylbutyl, 2-methylpentyl, l-methylhexyl, l-ethylpentyl, Z-ethylhexyl, 2-butylhexyl, and l-methyl- 4-ethyloctyl are suitable examples.

The employment of mixtures or orthosilicates or mixtures of alkoxysiloxanes or mixtures of orthosilicates and alkoxysiloxanes is advantageous to reduce crystallization. It is understood that lubricating compositions of our invention may contain varying amounts of other fluids such as mineral oils. In general, a final composition should contain at least 50 per cent by weight .of orthosilicate or alkoxysiloxane or of both so that the desirable properties of these fluids will be reflected in performance of the grease.

Mixtures of neutral fully esterified alkoxysiloxanes may be prepared by using condensed ethyl silicate as a starting material, and a mixture having the greatest degree of polymerization is preferred. The condensed ethyl silicaite preferably stripped of any residual orthosilicate by heating at reduced pressures. The stripped product is then added to a to excess ofthe' desired aliphatic alcohol. As the reaction proceeds, ethyl alcohol is evolved, and the resulting of stearic, oleic, palmitic, or similar fatty acids. n

The soap content may vary from 5 to 25 per cent with the optimum usually ranging within the narrower limits of 8 to 12 per cent, depending 'on the particular fluid selected or the grease properties desired. comprising, or containing laminated or foliated solids in a finelydivided condition, such as graphite, talc, carbon black, or the like, may be added to the soap-silicate compositions in various desired proportions.

An illustrative example-of a novel grease in accordance with our invention is:

Eighty-five and five-tenths arts of 2-ethylhexyl orthosilicate, 10 parts of lithium stearate, 4 parts of acrylic resin solution, phenyl-alpha-naphthylamine were mixed together at roomtemperature. The acrylic resin solution used was Acryloid HF 8555, a commeris frequently Compositions consisting of,

and part of cial product of Rohm and Haas Company, which is included to render the grease more compatible and homogeneous by decreasing the formation of crystals on cooling. The phenyl-alpha-naphthylamine is a representative aromatic amine type'oxidation inhibitor. The mixture was heate'drapidly with stirring until solubility was obtained at about 380 F. The solution was cooled rapidly by pouring into a water-cooled metal dish, and a gel structure formed after several minutes. The gel was broken to produce a smooth grease by passing it through a (SO-mesh wirescreen followed by several finer screens up to 200 mesh.

Another novel grease in accordance with our invention is:

Eightyseven and five-tenths parts of mixed decoxysiloxanes, prepared as described in our c0- pending application previously referred to, 12 parts of aluminum stearate, and part of N,N'- diphenylp-phenylenediamine, an oxidation inhibitor, were mixed at room temperature, and heated rapidly with stirring to about 275 F. when the components were miscible. Rapid cooling was performed by pouring the solution into a cooled metal dish, and a gel formed after several hours. The gel was broken by passing it through wire screens of successively finer mesh.

Thefinely dividedsolids describedabove may be added in these examples in desired propor- :tions.

not critical. In general, it is desirable to heat and cool the mixture as rapidly as possible and heating to the lowest temperature at which solubility is obtained is preferred.

It is apparent that any high molecular weight polymer which is soluble in an alkyl orthosilicate or an alkoxysiloxane and which has other generally desirable properties may be employed as the agent to'retard crystallization. The polymer content may vary from to 10 per cent.

Aromatic amine and phenol type oxidation inhibitors, such as phenyl-alpha-naphthylamine; phenyl beta naphthylamine; p tert butylphenol;.p hydroxy diphenylamine; N,N diphenyl' p phenylenediamine; p isopropoxydiphenylamine; N,l T' di beta naphthyl p phenylenediamine; p aminophenol; and diphenylamine; and other known inhibitors may be employed in our greases. The inhibitor content may vary from {-6 to 5 per cent.

The highand low-temperature performance characteristics of the greases of our invention are excellent and greatly superior to mineral oil greases in overall performance. For example, a grease prepared from Z-ethylhexyl orthosilicate and lithium stearate showed approximately a 1.5 per cent evaporation loss in the standard AN-G-25 test (Military Specification Greas Aircraft and Instruments, for Low and High Temperatures). This grease with oxidation inhibitors withstood a rigorous simulated service test for 3'30 hours, which performance is approximately equal to that of an AN-G-ZES specification product.

The allryl orthosilicates and alkoxysiloxanes may be combined with a number of different soaps and the examples are but illustrative. Such greases may also becoinpounded with a variety of different anti-crystallization agents, oxidation inhibitors, rust inhibitors, wear or extreme pressure additives, and the like.

It is now apparent to those skilled in the art that by the present invention we have provided novel grease compositions satisfyingthe objects above and that changes to the illustrative examples may be made without departing from our inventive concept. Reference should therefore be had to theappended claims to determine the scope of our invention.

What is claimed is:

l. A composition of matter, a grease containing per centto 75 per cent by weight of an alkyl orthosilicate and 5 per cent to 25 per cent by weight of soaps, said percentages totaling per cent.

2. A compositionof matter, a grease containing 95 per cent to '25 per cent by weight of alkyl orthosilicate, 5 per cent to 25 per cent by weight of soap, and small percentages of aromatic amine and phenoltype oxidationand acrylic'resin crystallization inhibitors, said percentages totaling lOi) per cent.

3. A compositionof matter, a grease containing 95 per. cent to'75 per cent by weight of an alkyl orthosilicate having from. 5 to 14 carbon atoms per hydrocarbon radical, and 5 per cent to 25 per cent by weight of soap, said percentages totaling 100 per cent.

4'. A composition ofmatter, a grease containing 95'per cent to '?5 per oentby weight of an organic silicate selected from the group consisting of alkyl' orthosilicates and alkoxysiloxanes, and 5 per cent to 25 per cent by weight of soaps, said percentages totaling 100 per cent.

1 5. A composition of matter, a grease containing 95 per cent to '75 per cent by weight of an organic silicate selected from the group consisting of alkyl orthosilicates and alkoxysiloxanes, 5 per cent to 25 per cent by weight of soap, and small percentages of aromatic amine and phenol type oxidation and acrylic resin crystallization inhibitors, said ercentages totaling 100 per cent.

6. A composition of matter, a grease containing 95 per cent to 75 per cent by weight of an organic silicate having from 5 to 14 carbon atoms in branched chain structure in the hydrocarbon radical selected from the group consisting of alkyl orthosilicates and alkoxysiloxanes, and 5 per cent to 25 per cent by weight of soap, said percentages totaling 100 per cent.

7. A composition of matter, a grease contain ing 95 per cent to 75 per cent by weight of an alkoxysiloxane and 5 per cent to 25 per cent by weight of soaps, said percentages totaling 100 per cent.

8. A composition of matter, a grease containing 95 per cent to 75 per cent by weight of an alkoxysiloxane, 5 per cent to 25 per cent by weight of soap, and small percentages of aromatic amine and phenol type oxidation and acrylic resin crystallization inhibitors, said percentages totaling 100 per cent.

9. A composition of matter, a grease containing 95 per cent to 75 per cent by weight of an alkoxysiloxane having from 5 to 14 carbon atoms in the hydrocarbon radical, and 5 per cent to 25 per cent by weight of soap, said percentages totaling 100 per cent.

10. A composition of matter, a grease containing a major amount by weight of an organic silicate selected from the group consisting of alkyl orthosilicates and alkoxysiloxanes, and minor amounts of soaps, mineral oils, and aromatic amine and phenol type oxidation and acrylic resin crystallization inhibitors.

11. A composition of matter, a grease containing a major amount by Weight of an organic silicate selected from the group consisting of alkyl orthosilicates and alkoxysiloxanes, and minor amounts of a laminated foliated solid in finely divided condition and soap.

12. A composition of matter, a grease containing a major amount by weight of an organic silicate selected from the group consisting of alkyl orthosilicates and alkoxysiloxanes, a minor amount of soap, and an aromatic amine oxidation inhibitor and of an acrylic resin solution crystallization inhibitor.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,053,474 Graves Sept.8, 1936 2,129,281 Lincoln et a1 Sept. 6, 1938 2,242,400 Loane May 20, 1941 2,274,673 Earle Mar. 3, 1942 2,403,104 Lien July 2, 1946 2,446,177 Hain Aug. 3, 1948 2,450,221 Ashburn Sept. 28, 1948 2,456,642 Merker Dec. 21, 1948 2,486,674 Pederson Nov. 1, 1949 2,490,691 Langkammerer Dec. 6, 1949 2,566,365 Pedlow et a1 Sept. 4, 1951 

1. A COMPOSITION OF MATTER, A GREASE CONTAINING 95 PER CENT TO 75 PER CENT BY WEIGHT OF AN ALKYL ORTHOSILICATE AND 5 PER CENT TO 25 PER CENT BY WEIGHT OF SOAPS, SAID PERCENTAGES TOTALING 100 PER CENT.
 11. A COMPOSITION OF MATTER, A GREASE CONTAINING A MAJOR AMOUNT BY WEIGHT OF AN ORGANIC SILICATE SELECTED FROM THE GROUP CONSISTING OF ALKYL ORTHOSILICATES AND ALKOXYSILOXANES, AND MINOR AMOUNTS OF A LIMINATED FOLIATED SOLID IN FINELY DIVIDED CONDITION AND SOAP. 